1. Field of the Disclosure
The invention relates to a video processing system.
2. Description of the Related Art
Electronic video processing or editing systems are used for example in television or film post production to modify video or film clips. The modifications which may be effected using such systems include the insertion of a first or foreground clip into a second or background clip either using a colour matte in one of the clips or using a separate control image or stencil. As used herein the term xe2x80x9cclipxe2x80x9d means a continuous (in time) sequence of video frames, unambiguously defined, from or in a single video source. Such systems can also be used to retouch one or more frames in a clip, to correct colours or to add texture to selected areas in the or each frame.
Hitherto known editing systems vary from manufacturer to manufacturer but generally comprise at least two video sources, for example video tape recorders (VTRs) whose outputs are connected to a vision mixer and which together with the vision mixer are controlled by an electronic edit controller. The system further comprises a monitor and during editing modified images are displayed thereon so that the user can see immediately the result of his modifications.
The system can be used to combine video clips from the two sources, which clips may be modified as described hereinabove prior to being combined. One way in which the clips may be combined is simply to join or splice one clip to the end of the other or to splice one clip or a portion of that clip into the middle of the other clip. In this mode of operation the edit controller is made responsive to an edit decision list which identifies the location of each clip in the two sources by for example its start frame and end frame, the number of frames in the clip and where appropriate the frames between which a splice is to be made.
A more sophisticated operation which may also be performed by the system is that of combining two clips by dissolving between the two clips. In a dissolving operation the edit decision list includes data identifying the number of frames in a dissolve. In response thereto the edit controller controls the mixer to combine corresponding frames in the two clips, for example in a weighted summing of the frame data. During this mode of operation frames from the source may be modified by an effects unit before being passed to the vision mixer. Thus, the system is operable to produce an xe2x80x9cedited clipxe2x80x9d, that is a sequence of concatenated clips joined together in a given order by way of edit transitions such as cuts, wipes and dissolves.
One disadvantage of such systems is that VTRs are sequential access devices and cannot simultaneously playback and record different video clips. This means that a separate VTR is required as a source for each video clip to be worked on and at least one further VTR is required to record the video output from the mixer.
We manufacture a video processing and editing system which is currently sold under the trade mark xe2x80x9cHENRYxe2x80x9d. The principles behind our HENRY editing system are described in detail in our British Patent Application Publication No. GB-A-2266037 and corresponding U.S. application Ser. No. 08/467,755, the teachings of which are incorporated herein by reference. The HENRY system comprises among other things a store having several disc drives for storing multiple video frames in random access order. The store also is arranged to enable data to be transferred therefrom at video rate. This allows the system to operate in a preview mode in which video clips are read from the store modified and/or combined and displayed on a monitor at video rate without the need to commit the modification or combination to the store beforehand.
Further features of our HENRY editing system include the displaying of multiple clips with selected clips being arranged on the display in the form of a pack of clips, that is to say two or more video clips which provide background and foreground images when combined in a video clip and which can be manipulated like a pack of cards so as to change the order in which the images are laid onto one another. The system assigns a priority to each of the clips in the pack according to its position therein and the priority is used subsequently in the combining of the clips. In addition to simple splice and dissolve operations by which two clips are combined, our HENRY editing system is able to combine two or more clips in a priority order over several frames.
Thus, in addition to producing an edited clip, the HENRY editing system is able to produce a layered clip comprising a number of clips with frames coincident in time, combined in a given order of priority. Each clip in the layered clip may have associated with it attributes which determine effect moves, keying parameters, texture control, motion control, and indeed any data that is pertinent to manipulation of the video image of the clip.
Once the user is satisfied with the edited or layered clip as created in the preview mode, the user is able to command the system to commit to the edited or layered clip. The system is arranged to respond to such a command by combining the video data for the initial clips that contribute to the edited or layered clip to produce a resultant clip. Our HENRY editing system has hitherto handled the three entities, namely clips, layered clips and edited clips as being entirely separate and independent. That is to say, once the user has committed to the resultant clip and the data has been combined, the resultant clip has no information associated with it identifying the initial clips or how they contributed to the resultant clip. The resultant clip is treated by the system like any other clip. Thus, the resultant clip, once created, may be used as an initial clip that contributes to another edited or layered clip.
While such an approach clearly offers great flexibility in producing a complex resultant clip from multiple initial clips, it suffers from the problem that once a commitment has been made it is not possible at a later stage to go back into a clip and modify the way in which that clip is produced from initial clips. If an error has been made and the appearance of the clip is, say, not quite what was required, then the only way to correct the error is to discard the clip and start again from the initial clips. It may not always be possible to reproduce all aspects of the discarded clip that are still required. For example the user may not know exactly which colour correction to apply to an area in one of the initial clips, or it may be difficult to determine exactly which frames mark the end of one clip and the beginning of another in a dissolve edit. Clearly, this is undesirable.
The present invention aims to overcome or at least reduce the above and associated problems.
According to one aspect of the invention there is provided a video processing system in which video data representing a plurality of clips has associated with each of the clips a set of clip data comprising process data identifying processing to be applied to the video data in the production of another clip and history data identifying the origin of the clip.
According to another aspect of the invention there is provided a video processing apparatus, comprising: a video store for storing video data defining a plurality of clips; a data store for storing for each of the clips an associated set of clip data comprising process data identifying processing to be applied to the video data forming the clip and history data identifying the origin of the clip; and a processor for processing the video data forming a clip or clips in accordance with the processing identified by the process data associated with the or each clip to produce video data forming a processed clip for storage in the video store and an associated set of clip data for storage in the data store.
According to a further aspect of the invention there is provided a video processing method, comprising: storing video data defining a plurality of clips in a video store; storing in a data store for each of the clips an associated set of clip data comprising process data identifying processing to be applied to the video data forming the clip and history data identifying the origin of the clip; and processing the video data forming a clip or clips in accordance with the processing identified by the process data associated with the or each clip to produce video data forming a processed clip for storage in the video store and an associated set of clip data for storage in the data store.